react-router4 嵌套路由

import React from ‘react‘;
import ReactDOM from ‘react-dom‘;
import { HashRouter as Router, Route, Switch} from ‘react-router-dom‘;
import createBrowserHistory from ‘history/createBrowserHistory‘;
import UserAddPage from ‘./pages/UserAdd/index‘;
import HomePage from ‘./pages/Home/index‘;
import HomeLayout from ‘./components/HomeLayout/index‘;

const hashHistory = createBrowserHistory();
const NoMatch = ({ location }) => (
  <div>
    <h3>无法匹配 <code>{location.pathname}</code></h3>
  </div>
)
ReactDOM.render((
  <Router history={hashHistory}>
    <div>
      <HomeLayout>//总会加载这个组件，并且下面 swicth 里面的组件会在它里面 render 
        <Switch>
          <Route path="/" exact component={HomePage}/>
          <Route path="/user/add" component={UserAddPage}/>
          <Route component={NoMatch}/>
        </Switch>
      </HomeLayout>
    </div>
  </Router>
), document.getElementById(‘root‘));